Thanks for the response. I have not set CC to clean AVG as I didn't delve that far into the CC settings. I did save the helper app and instructions for it. When I first searched the AVG website for data regarding the CTF file I used the website's main search engine. Nothing shows up via that route. When I returned to the website today I input the error text into the FAQs search engine and I found the helper app. Through your comments I feel somewhat relieved to know I am not alone in dealing with this glitch. And as you say, it is easy to rectify now that I know how.
I noticed the discussion regarding "avg anti virus doesn't like downloads" and wonder if the AVG notification I am shown when it attempts to update is caused by CCleaner deleting some aspect of the AVG "update control CTF file." I am using AVG v8.0.175 on WinVista v6.0.6001 w/Service Pack 1Build 6001 I have encountered this problem several times now. After the first time I was unable to use AVG's automatic update, I went to their website and manually downloaded the latest virus definitions file. Upon restarting my computer the next time after that session I again encountered the "Invalid u